1 September 1991 Symmetry properties of reverse-delta-beta directional couplers
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Directional couplers based on titanium-diffused lithium niobate are potentially attractive for applications requiring polarization-independent optical switching or modulation. Although directional couplers with >25 dB switching extinction ratio for both TE and TM modes have been fabricated, polarization independence and reproducibility are difficult to achieve. Presumably, uncontrollable process variations result in different coupling strengths and switching characteristics in nominally identical devices. These variations can be compensated by using the so-called reverse-(Delta) (beta) design, where the device electrodes are split into two different sections and tuned with separate voltages to obtain maximum cross-state extinction. The addition of a second control voltage complicates characterization of the devices, since full characterization requires plotting switching in a two-dimensional voltage space. The authors have developed a system to automatically perform two-dimensional switch characterizations. The resulting data display asymmetries which can be analyzed within the framework of coupled mode theory. The analyses indicate that two factors contribute to the observed asymmetry: a static, fabrication-induced difference in propagation constant (beta) between the two waveguides, and an applied-field dependent evanscent coupling strength.
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Terry L. Smith, Terry L. Smith, David K. Misemer, David K. Misemer, Daniel V. Attanasio, Daniel V. Attanasio, Gretchen L. Crow, Gretchen L. Crow, Wiley K. Smith, Wiley K. Smith, Mary J. Swierczek, Mary J. Swierczek, James E. Watson, James E. Watson, } "Symmetry properties of reverse-delta-beta directional couplers", Proc. SPIE 1512, Infrared and Optoelectronic Materials and Devices, (1 September 1991); doi: 10.1117/12.47151; https://doi.org/10.1117/12.47151

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